1. Field of the Invention
This invention relates to corona generators and in particular to commercial large scale ozone generators.
2. Description of the Prior Art
Present commercial ozone generators (as distinguished from very small and inefficient generators capable of producing less than one pound of ozone a day) are used primarily in certain chemical processes and other applications requiring a high degree of sterilization, unobtainable by the use of well-known chemical oxidants or disinfectants. Although beneficial in many other major applications, such as treatment of industrial waste water or sewage, for example, commercial ozone generators are not used extensively, because the ozone is produced in a highly diluted form by equipment that is costly, bulky, complicated, and expensive to operate. According to the accepted and usual practice in commercial ozone generators, the corona discharge for producing ozone is generated by applying a voltage in the order of from ten thousand to twenty thousand volts across a glass tube, having walls approximately 100 mils thick, with a conductive coating on the inside, and a metallic conductor adjacent the tube's outside surface. In such apparatus, operating at 15,000 volts, for example, the actual ozone ouput is in the order of less than 2 ounces per day per square foot of generating area under normal atmospheric conditions. Further, such bulky apparatus requires water cooling and thousands of gallons of water must be pumped through the apparatus daily. Attempts have been made to make commercial ozone generators employing, for example, mica, oil paper, plastic, glass, and rubber dielectrics, either as separate sheets or coated onto an electrode by immersion or painting, but all such attempts have failed because, for example, either a high voltage application was required to obtain even minimal amounts of ozone, or there were limitations in the configurations that the generating devices could assume, or the dielectric would burn through after a limited number of hours of operation.
It is an object of the present invention to provide a new corona generator method and apparatus that overcomes the problems of previous corona generators, and that produces large amounts of high concentration ozone without water cooling and at relatively low voltages. The present invention teaches the importance of using a thin, hard porcelain enamel dielectric coating free of bubbles and free of conductive particles, and also of minimizing the dielectric thickness and maximizing the dielectric constant to produce an unexpected substantial increase in useful corona power per unit of dielectric area, and thus a corresponding increase in ozone yield. For example, for a given dielectric constant and voltage a 5 mil dielectric produces eight times as much ozone as a 40 mil dielectric, and 20 times as much as the usual 100 mil dielectric, operated according to the previous method. Also, for a given voltage, a 5 mil dielectric with a dielectric constant of 100, for example, produces 400 times more ozone than a conventional 100 mil glass dielectric for a given dielectric surface area. Additionally, by using a fired-on porcelain enamel dielectric coating with a high temperature softening point, a reliable, long lasting assembly is provided, and at the same time, the ozone output per unit of dielectric generating area is substantially increased for a given voltage.
A further object of the present invention is to provide an improved corona generator for producing ozone, that is inexpensive, durable, rugged and relatively simple to manufacture.